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We extract interstellar scintillation parameters for pulsars observed by theNANOGrav radio pulsar timing program. Dynamic spectra for the observing epochsof each pulsar were used to obtain estimates of scintillation timescales,scintillation bandwidths, and the corresponding scattering delays using astretching algorithm to account for frequency-dependent scaling. We were ableto measure scintillation bandwidths for 28 pulsars at 1500 MHz and 15 pulsarsat 820 MHz. We examine scaling behavior for 17 pulsars and find power-lawindices ranging from $-0.7$ to $-3.6$, though these may be biased shallow dueto insufficient frequency resolution at lower frequencies. We were also able tomeasure scintillation timescales for six pulsars at 1500 MHz and seven pulsarsat 820 MHz. There is fair agreement between our scattering delay measurementsand electron-density model predictions for most pulsars. We derive interstellarscattering-based transverse velocities assuming isotropic scattering and ascattering screen halfway between the pulsar and earth. We also estimate thelocation of the scattering screens assuming proper motion and interstellarscattering-derived transverse velocities are equal. We find no correlationsbetween variations in scattering delay and either variations in dispersionmeasure or flux density. For most pulsars for which scattering delays weremeasurable, we find that time of arrival uncertainties for a given epoch arelarger than our scattering delay measurements, indicating that variablescattering delays are currently subdominant in our overall noise budget but areimportant for achieving precisions of tens of ns or less.

The NANOGrav 12.5-Year Data Set: Monitoring Interstellar Scattering Delays